In order to enhance the production efficiency, there is a type of substrate processing apparatus that collectively processes a plurality of substrates. For example, in this type of substrate processing apparatus, the plurality of substrates is circumferentially arranged in a single process chamber.
In this case, the substrates are processed by supplying a gas to the process chamber to form a film on each of the substrates. When processing the substrates, the gas is supplied under preset conditions.
In the substrate processing apparatus, it is required to improve yield. Thus, each of the substrates is processed to maintain a constant quality in the plane of the substrates. Furthermore, each of the substrates is processed to maintain a constant quality with high reproducibility.
In order to maintain this constant quality, it is desirable to set the state of the process chamber in which the substrates are processed to fall within a predetermined range. To do so, it is required to more accurately recognize the state of the process chamber.